1. Field of Invention
The present invention relates to a projector for projecting and displaying an image.
2. Description of Related Art
In projectors, light emitted from an illuminating optical system is modulated according to image information (image signals) with the use of a liquid crystal light valve or the like, and the modulated light is projected onto a screen, thereby achieving image display.
The liquid crystal light valve commonly includes a liquid crystal panel and a polarizer formed on the side of a light incidence surface or on the side of a light emission surface. The polarizer transmits only a light component in a direction of a polarization axis and intercepts other light components. This will modulate the light incident on the liquid crystal light valve according to image information.
The polarizer commonly generates heat when it intercepts light other than a light component in the direction of the polarization axis. When the temperature of the polarizer is raised by the generation of heat, the polarizer is strained or deteriorated, and the polarizer transmits light that should not be transmitted or intercepts light that should not be intercepted. In order to reduce the temperature rise, the polarizer has been provided on a single-crystal sapphire substrate having high heat conductivity.
FIG. 10 is an illustration showing a conventionally used single-crystal sapphire substrate 908. A polarizer 902 is bonded on a single-crystal sapphire substrate 908 as shown by broken lines in the figure. The single-crystal sapphire substrate 908 and the polarizer 902 are formed according to an effective display area of a liquid crystal panel having nearly a rectangular shape, so that the single-crystal sapphire substrate 908 and the polarizer 902 have nearly a rectangular shape.
The single-crystal sapphire substrate 908 includes a c-axis substantially parallel to the surface of the substrate. In addition, the c-axis is substantially parallel to a side s1 selected from perpendicularly intersecting two sides s1 and s2 of the nearly rectangular shape. Specifically, the single-crystal sapphire substrate 908 is accurately formed so that an inclination angle xcex8 of the c-axis with respect to the reference side s1 of the substrate falls within about 10xc2x0.
Such a single-crystal sapphire substrate having high c-axis accuracy is used in the conventional projector in order not to change too much the polarization state of light passing through the single-crystal sapphire substrate. The use of such a single sapphire substrate can provide excellent maintenance of optical characteristics of the projector.
However, much labor is required to manufacture such a single-crystal sapphire substrate 908 having high c-axis accuracy and, consequently, much labor is required to manufacture a projector using the single-crystal sapphire substrate 908 having high c-axis accuracy. This is because, in order to obtain a single-crystal sapphire substrate having high c-axis accuracy, an adjusting procedure should be repeatedly performed such that the inclination angle xcex8 of the c-axis is measured by X-ray diffraction or the like after producing a single-crystal sapphire substrate having relatively low c-axis accuracy and further, the sapphire glass substrate is polished.
This invention is made to solve the above-described problems in the conventional art. One object of the various embodiments of the invention is to provide a technique capable of easily manufacturing a projector without deteriorating too much the optical characteristics of the projector.
In order to solve at least a part of the above-described problems, according to a first embodiment of the present invention, there is provided a projector including:
an illuminating optical system that emits illumination light;
an electro-optical device that modulates light from the illuminating optical system according to image information; and
a projection optical system that projects a modulated light beam flux obtained by the electro-optical device;
wherein the electro-optical device includes a single-crystal sapphire substrate having a substantially rectangular shape disposed on at least one side of a light incidence surface and a light emission surface; and
a polarizer provided on the single-crystal sapphire substrate;
the single-crystal sapphire substrate includes a c-axis substantially parallel to the surface of the substrate; and
the c-axis has an inclination of about 3xc2x0 to about 7xc2x0 with respect to one reference side selected from perpendicularly intersecting two sides of the nearly rectangular shape.
In the projector of the present invention, the polarizer is provided on the single-crystal sapphire substrate having the c-axis inclined about 3xc2x0 to about 7xc2x0 with respect to the reference side of the nearly rectangular shape. The use of such a single-crystal sapphire substrate makes it possible to easily manufacture the projector without deteriorating too much the optical characteristics of the projector.
In the above device, the polarizer may be provided on the single-crystal sapphire substrate so that the polarization axis thereof is substantially parallel to or perpendicular to the reference side.
If the polarizer is provided on the single-crystal sapphire substrate in this way, the relationship between the c-axis of the substrate and the polarization axis of the polarizer can be set to be substantially parallel to or perpendicular to each other. This makes it possible to reduce the change in the polarization state of light due to the passage through the single-crystal sapphire substrate.
In the above device, the polarizer formed on the single-crystal sapphire substrate may be provided on the side of the light emission surface of the electro-optical device, and
the single-crystal sapphire substrate and the polarizer may be disposed so that light emitted from the polarizer enters the single-crystal sapphire substrate.
In addition, in the above device, the polarizer formed on the single-crystal sapphire substrate may be provided on the side of the light incidence surface of the electro-optical device, and
the single-crystal sapphire substrate and the polarizer may be disposed so that light emitted from the single-crystal sapphire substrate enters the polarizer.
If the single-crystal sapphire substrate and the polarizer are disposed in this order, the polarization state of light is changed by passing through the single-crystal sapphire substrate, but lowering of contrast of an image light (modulated light) is avoided.
According to a second embodiment of the present invention, there is provided a projector that projects and displays a color image, including:
an illuminating optical system that emit illumination light;
a color light separation optical system that separates the illumination light emitted from the illuminating optical system into first to third color lights having three color components;
first to third electro-optical devices that modulate the first to third color lights separated by the color light separation optical system according to image information to produce first to third modulated light beam fluxes;
a color synthesizing section that synthesizes the first to third modulated light beam fluxes; and
a projection optical system that projects synthesized light emitted from the color synthesizing section;
wherein each of the first to third electro-optical devices includes a single-crystal sapphire substrate having a substantially rectangular shape disposed on at least one side of a light incidence surface and a light emission surface; and
a polarizer provided on the single-crystal sapphire substrate;
the single-crystal sapphire substrate includes a c-axis substantially parallel to the surface of the substrate; and
the c-axis has an inclination of about 3xc2x0 to about 7xc2x0 with respect to one reference side selected from perpendicularly intersecting two sides of the nearly rectangular shape.
In this projector, the polarizer is also provided on the single-crystal sapphire substrate having the c-axis inclined about 3xc2x0 to about 7xc2x0 with respect to the reference side of the nearly rectangular shape, so that it is possible to easily manufacture the projector without deteriorating too much the optical characteristics of the projector.